1. Field of the Invention
The present invention relates to a liquid printer, and more particularly, to an apparatus for elevating a squeegee roller and a development roller, for adjusting their setting positions relative to a photosensitive medium by adaptively elevating the squeegee roller and the development roller according to the operation mode of the printer.
2. Description of the Related Art
As shown in FIG. 1, a liquid printer such as a color laser printer includes a development device for supplying a developer liquid to an electrostatic latent image formed on a transfer surface 10a of a photoreceptor belt 10 as a photosensitive medium.
The development device includes a development roller 11 for transferring a developer liquid supplied from a developer liquid spray nozzle 15 to the transfer surface 10a of the photoreceptor belt 10. A backup roller 14 is positioned opposite development roller 11. In the downstream side of the development roller 11, there is a squeegee roller 12 for removing a carrier contained in the developer liquid transferred on the transfer surface 10a of the photoreceptor belt 10 by pressing the photoreceptor belt 10 toward a backup roller 13.
As the printing operation is repeatedly carried out, the developer liquid may accumulate and coagulate on a contact portion of the photoreceptor belt 10 and the squeegee roller 12, thereby forming a drip line (D).
Thus, in order to obtain a clean-quality printed image, it is necessary to remove the drip line D at regular time intervals during the printing operation. The drip line D is removed in a drip line removal mode in which the squeegee roller 12 is driven in a reverse direction to the rotating direction thereof in a printing mode.
In the drip line removal mode, in order to reduce a rotation load due to the reverse rotation of the squeegee roller 12, the squeegee roller 12 is lowered by an elevating apparatus shown in FIG. 2. Then, the squeegee roller 12 presses the photoreceptor belt 10 at a lower level position than in the printing mode, thereby decreasing the compressive force. After the printing operation is terminated, the elevating apparatus lowers both the squeegee roller 12 and the development roller 11, so that they are completely detached from the photoreceptor belt 10. In other words, the elevating apparatus elevates the development roller 11 and the squeegee roller 12 adaptively according to the operation mode of the printer, thereby adjusting their setting positions relative to the photoreceptor belt 10.
Referring to FIG. 2 showing the apparatus for elevating a development roller and a squeegee roller, which is installed in the conventional development device, a pair of sub-blocks 21 and 22 are installed to be elastically biased by compression springs 24 installed on the bottom of a main block 20. A slider 23 which linearly reciprocates is installed in the main block 20. A development roller 11 and a squeegee roller 12 are rotatably installed at the top ends of the sub-blocks 21 and 22, respectively.
The slider 23 it is elastically biased in one direction by a torsion spring 26 installed at one end thereof and linearly reciprocates by the operation of a cam 25 connected to a driver (not shown) installed at the other end thereof. Also, cam slots 23a and 23b having different shapes from each other are formed at locations substantially corresponding to those of the sub-blocks 21 and 22. Cam studs 22a and 22b protruding on the respective sub-blocks 21 and 22 are inserted into the cam slots 23a and 23b.
According to the elevating apparatus having the aforementioned construction, as the slider 23 moves to the left and right, the cam studs 22a and 22b of the sub-blocks 21 and 22 are guided by the cam slots 23a and 23b thereby elevating the sub-blocks 21 and 22 by the elastic action of the torsion spring 26 and the compression spring 24. Accordingly, the sub-blocks 21 and 22, and the development roller 11 and the squeegee roller 12 respectively installed on the top ends thereof, elevate in engagement with each other.
According to the above-described conventional elevating apparatus, it is difficult to make the overall printer system more compact, due to the space required for linear reciprocation of the slider 23.